α,α-Dialkylglycines obtained by solid phase Ugi reaction performed over isocyanide functionalized resins

The multicomponent Ugi reaction is a straightforward method that can be used for the synthesis of highly hindered C-tetrasubstituted amino acids by reacting an amine, a ketone or aldehyde, a carboxylic acid and an isocyanide. In the present work, the synthesis of several α,α-dialkylglycines (α,α-diethylglycine, Deg; α,α-dipropylglycine, Dpg; 1-amino-1-cyclohexanecarboxylic acid, Ac₆c) was achieved by solid phase Ugi reaction using resins functionalized with the isocyanide group. Since no resins with these features were available commercially, the functionalization of an aminomethylated resin started by the use of glycine (Gly), β-alanine (β-Ala) and γ-aminobutyric acid (GABA) as spacers. After spacer N-formylation, followed by dehydration, isocyanide functionalised resins were obtained. The resins were then used in solid phase Ugi reaction, using phenylacetic acid as the acid component, 4-methoxybenzylamine as the amine component and different ketones, to afford the desired N-acylated α,α-dialkylglycines in good overall yields (60–80%), after acidolytic cleavage from the resin, thus proving the feasibility of this approach.     

Antioxidant, Anti-inflammatory, and Hypoglycemic Effects of the Leaf Extract from Passiflora nitida Kunth

Diabetes mellitus is a metabolic disease characterized by abnormally high plasma glucose levels, leading to major complications, such as insulin resistance, obesity, hyperlipidemia, and hypertension, also with alterations in the immune and neuronal systems. Brazilian plants have been studied as important sources for new molecules with medicinal properties. The genus Passiflora known as “Maracujá” has been used as a traditional folk medicine for a long time, so an investigation was performed regarding an endemic kind of passion fruit (Passiflora nitida Kunth) from Amazonas, Brazil. Here, we aimed to determine its potential biological activity against metabolic syndrome, oxidative stress, pain, and inflammation. The hydroethanol leaf extract revealed an in vitro α-glucosidase inhibitory activity of 50 % inhibitory concentration (IC₅₀)?=?6.78?±?0.31 μg/mL and an α-amylase inhibition of IC₅₀?=?93.36?±?4.37. In vivo, experiments of different saccharide tolerance resulted in significant glycemia control and, with alloxan-diabetic mice, resulted in a decrease of total cholesterol, a hypoglycemic effect, and an antioxidant activity by thiobarbituric acid-reactive substances measurement. Also, it decreased the carrageenan-induced edema volume and the rate of writhing as a nociceptive response. These results indicate positive effects of P. nitida extract and its potential to inhibit metabolic syndrome.     

Wetting behavior of pulmonary surfactant aqueous solutions

The wetting properties of pulmonary surfactant aqueous solutions with respect to solid surfaces with different degree of hydrophobicity have been studied. The contact angles θ of drops from a pulmonary surfactant solution onto SiO₂-glass surfaces have been measured as a function of their degree of hydrophobicity θ _w. The completely hydrophilic SiO₂-glass surface is essentially hydrophobized by the animal-derived pulmonary surfactant Curosurf. The hydrophobization depends on the surfactant concentration—the contact angles increase with increasing the Curosurf concentration C _s in the low concentration range, but they remain almost constant in a wide range of C _s >90 μg/ml. Additions like NaCl and bovine serum albumin influence the θ-values. The contact angles θ naturally increase with increasing θ _w but this dependence is not linear—the curve steepens at larger θ _w values. The thickness h of the wetting thin liquid films from Curosurf aqueous solutions depends on the hydrophobicity θ _w of the solid surface and the h(θ _w) curves always pass a minimum. The h-values, as well as the h(θ _w) curve, are mainly determined by the steric and hydrophobic disjoining pressures, which depend on the orientations and conformations of the molecules adsorbed on the solid surface from the very complicated multi-component aqueous solutions.     

The effects of lignin removal and drying on the porosity and enzymatic hydrolysis of sugarcane bagasse

The porosity of lignocellulosic materials is a key feature for the enzymatic hydrolysis of the constituent polysaccharides, being affected by its drying and lignin content. Here we evaluated the influence of both parameters in the porosity of sugarcane bagasse, using raw and chlorite-delignified samples. A fraction of these samples was air dried at room temperature and the remainder one was kept wet. All the samples were subjected to porometry (solute exclusion technique), determination of water retention value and assessment of enzymatic saccharification of polysaccharides. Samples with higher lignin contents had lower porosities and exhibited worse enzymatic conversions of polysaccharides. Mild drying collapsed only the smaller pores, which already were inaccessible to enzymes, and therefore did not affect the efficiencies of saccharification. Our results show that the lignin content plays an important role in the porosity of the material and that its removal improves the enzymatic saccharification of the constituent polysaccharides.     

Synthesis of 3-iodothiophenes via iodocyclization of (Z)-thiobutenynes

A simple synthesis of 3-iodothiophenes was demonstrated using a wide range of (Z)-thioenynes. The key step in the iodocyclofunctionalization was the selective reduction of the triple bond in (Z)-thioenynes by the addition of iodine as an electrophilic agent. The 3-iodothiophenes were obtained in good to excellent yields of 61–92%. The 3-iodothiophenes were used as substrates in Sonogashira cross-coupling reactions to obtain thiophene acetylenes.     

Radioanalytical assessment of environmental contamination around non-remediated uranium mining legacy site and radium mobility

During the past century extensive uranium mining took place in Portugal for radium and uranium production. One such uranium mine was the Boco Mine, in operation during the 1960s and 70s. Mining waste and open pits were left uncovered since mine closure. During the nineties a quarry for sand extraction was operated in the same site and water from a local stream was extensively used in sand sieving. Downstream the mine area, agriculture soil is used for cattle grazing. Water from the stream, water wells, soil, pasture and sheep meat were now analyzed for radionuclides of uranium natural series. The U-series radionuclide ²²⁶Ra was generally the highest in concentrations especially in soil, pasture, and in internal organs of sheep. ²²⁶Ra concentrations were 1,093 ± 96 Bq/kg (dry weight, dw) in soil, 43 ± 3 Bq/kg (dw) in pasture, and 193 ± 84 mBq/kg (wet weight, ww) in muscle tissue of sheep. Other sheep internal organs displayed much higher ²²⁶Ra concentrations, such as the brain and kidneys with 1,850 ± 613 mBq/kg (ww) and 6,043 ± 6,023 mBq/kg (ww), respectively. Results of analyses of tissue samples from sheep grown in a comparison area were 2 to 16 times lower, depending on the organ. Absorbed radiation doses for internal organs were computed and may exceed 5.2 mGy/y in the case of kidneys, near three times higher than in animals from the reference area, but below the threshold for biological effects. Radionuclide transfer in the terrestrial food chain and radiation exposure of the human population is discussed.     

Grafting amount and structural characteristics of microcrystalline cellulose functionalized with different aminosilane contents

Cellulose - Microcrystalline cellulose (MCC) has unique properties and its use as reinforcement for polymer composites has been increasing. However, the intrinsic incompatibility with most polymers...     

Zn-Induced Interactions Between SARS-CoV-2 orf7a and BST2/Tetherin

We present in this work a first X-ray Absorption Spectroscopy study of the interactions of Zn with human BST2/tetherin and SARS-CoV-2 orf7a proteins as well as with some of their complexes. The analysis of the XANES region of the measured spectra shows that Zn binds to BST2, as well as to orf7a, thus resulting in the formation of BST2-orf7a complexes. This structural information confirms the the conjecture, recently put forward by some of the present Authors, according to which the accessory orf7a (and possibly also orf8) viral protein are capable of interfering with the BST2 antiviral activity. Our explanation for this behavior is that, when BST2 gets in contact with Zn bound to the orf7a Cys₁₅ ligand, it has the ability of displacing the metal owing to the creation of a new disulfide bridge across the two proteins. The formation of this BST2-orf7a complex destabilizes BST2 dimerization, thus impairing the antiviral activity of the latter.     

Antiprotozoal and Antibacterial Activity of Ravenelin,a Xanthone Isolated from the Endophytic Fungus Exserohilum rostratum

The natural compound ravenelin was isolated from the biomass extracts of Exserohilum rostratum fungus, and its antimicrobial, antiplasmodial, and trypanocidal activities were evaluated. Ravenelin was isolated by column chromatography and HPLC and identified by NMR and MS. The susceptibility of Gram-positive and Gram-negative bacteria strains to ravenelin was determined by microbroth dilution assay. Cytotoxicity was evaluated in hepatocarcinoma cells (HepG2) and BALB/c peritoneal macrophages by using MTT. SYBR Green I-based assay was used in the asexual stages of Plasmodium falciparum. Trypanocidal activity was tested against the epimastigote and intracellular amastigote forms of Trypanosoma cruzi. Ravenelin was active against Gram-positive bacteria strains, with emphasis on Bacillus subtilis (MIC value of 7.5 µM). Ravenelin’s antiparasitic activities were assessed against both the epimastigote (IC₅₀ value of 5 ± 1 µM) and the intracellular amastigote forms of T. cruzi (IC₅₀ value of 9 ± 2 µM), as well as against P. falciparum (IC₅₀ value of 3.4 ± 0.4 µM). Ravenelin showed low cytotoxic effects on both HepG2 (CC₅₀ > 50 µM) and peritoneal macrophage (CC₅₀ = 185 ± 1 µM) cells with attractive selectivity for the parasites (SI values > 15). These findings indicate that ravenelin is a natural compound with both antibacterial and antiparasitic activities, and considerable selectivity indexes. Therefore, ravenelin is an attractive candidate for hit-to-lead development.     

Structural Evidence for Pnictogen-Centered Lewis Acidity in Cationic Platinum-Stibine Complexes Featuring Pendent Amino or Ammonium Groups

As part of our continuing interest in the chemistry of cationic antimony Lewis acids as ligands for late transition metals, we have now investigated the synthesis of platinum complexes featuring a triarylstibine ligand substituted by an o-[(dimethylamino)methyl]phenyl group referred to as Ar^N. More specifically, we describe the synthesis of the amino stibine ligand Ph₂SbAr^N (L) and its platinum dichloride complex [LPtCl]Cl which exists as a chloride salt and which shows weak coordination of the amino group to the antimony center. We also report the conversion of [LPtCl]Cl into a tricationic complex [LHPt(SMe₂)]³⁺ which has been isolated as a tris-triflate salt after reaction of [LPtCl]Cl with SMe₂, HOTf and AgOTf. Finally, we show that [LHPt(SMe₂)][OTf]₃ acts as a catalyst for the cyclization of 2-allyl-2-(2-propynyl)malonate.